In conversations with participants, there was a lot of interest in the emerging fact that even moderate noise levels can have a dramatic effect on animals nearby. I stressed the point that while noise may rarely be a primary factor in animal impacts, the increased stress caused by dealing with elevated noise levels can often create synergistic effects that amplify the effects of other known impacts.

My detailed poster introduced what is known about individual variability to noise within animal populations, summarized some impacts of moderate noise on wildlife, explained noise levels around wind farms, and suggested several situations in which noise impacts on a more-sensitive subset of the local population could be a factor in wind farm impact planning (click image to view on SlideShare, or click full screen to view larger):

Zion National Park has become the first of its brethren to adopt a formal Soundscape Management Plan, the culmination of three years of work. For the first time, soundscape measurement metrics that have been in development at the NPS Natural Sounds Program office in Ft. Collins, Colorado, will be driving forces in ongoing Park management and assessment procedures. One of these metrics is the “noise-free interval,” or average time between the audible presence of human sound. According to Frank Turina, an NPS Natural Sound Program planner, “Now it’s two to three minutes before you hear a human-caused sound, usually involving an overflight, and we want to expand that to a seven-minute period. If we meet that goal we will reassess the situation to see if a longer interval is warranted.”

While some environmental groups had pushed for the Park Service to set a higher standard for back country visitors, this first step, if successful, would effectively reduce sound intrusions to less than half their current level. And the fact is, even this first step will depend on cooperation from the Federal Aviation Administration, which has so far been slow to take on the necessary shared responsibility for National Park overflight issues.

In more active areas of the Park, such as around visitor centers and within the first mile of trailheads, where the vast majority of visitors spend their time, the goal is to reduce noise by changing some Park staff and maintenance procedures. For example, the use of leafblowers may be reduced in favor of rakes, and new vehicles will be assessed for possible noise-reduction systems. “Surveys have shown that 90 percent of people who visit the national parks want natural quiet and to be able to hear the sounds of nature,” said Kezia Nielson, who worked on the plan. “They cannot have that experience with human-caused sound.”